#! usr/bin/node

const log = console.log,
      argv = process.argv[2];

if(typeof(argv) === 'undefined' || 
    argv === '--help' || 
    argv === '-h'){
  help();
}else{
  calc();
}
function help(){
  const msg = 'something about help...';
  log(msg);
}
function calc(){
  try{
    log(`${argv} = ${eval(argv)}`);
  }catch(e){
    log(`${argv} 是非法的表达式`);
  }
}

// nide 02-cacl.js 3+4
